Title: Installed Performance Assessment of an Array of Distributed Propulsors Ingesting Boundary Layer Flow
Abstract: Conventional propulsion systems are typically represented as uninstalled system to suit the simple separation between airframe and engine in a podded configuration. However, boundary layer ingesting systems are inherently integrated, and require a different perspective for performance analysis. Simulations of boundary layer ingesting propulsions systems must represent the change in inlet flow characteristic which result from the local flow condition. In addition, a suitable accounting system is required to split the airframe forces from the propulsion system forces. The research assesses the performance of a conceptual vehicle which applies a boundary layer ingesting propulsion system — NASA’s N3-X blended wing body aircraft — as a case study. The performance of the aircraft’s distributed propulsor array is assessed using a performance method which accounts for installation terms resulting from the boundary layer ingesting nature of the system. A ‘thrust split’ option is considered which splits the source of thrust between the aircraft’s main turbojet engines and the distributed propulsor array. An optimum thrust split for a specific fuel consumption at cruise is found to occur for a thrust split value of 93%, for the configuration considered. In comparison, the optimum thrust split with respect to fuel consumption for the design 7500 nmi mission is found to be 91.5%. Aircraft performance estimates suggest the N3-X could achieve a maximum payload range of approximately 13650 nautical miles.